Mobile snooping may soon become a reality for many as researchers have demonstrated a technique which uses $15 mobile phones, a laptop and open source software to spy on calls and text messages sent on GSM networks.

At the Chaos Computer Club (CCC) Congress, researchers Karsten Nohl and Sylvain Munaut demoed a technique which can be used by a fairly capable computer programmer to spy on calls and text messages on GSM mobiles.

The new GSM hack works with the hackers first zeroing in on the location of a particular subscriber, exploiting the way in which GSM networks exchange subscriber data. Once that it done, the hackers then drive around sending 'silent' text messages to the target device, which don't show up on a mobile device.

Next, using cheap Motorola GSM, which carry specially designed firmware, hackers can snoop into the raw data which is sent to the target mobile phone from the network.

“GSM is insecure, the more so as more is known about GSM. It’s pretty much like computers on the net in the 1990s, when people didn’t understand security well,” Nohl said.